I wouldn't really expect your personnel ages to leave the range of an unsigned octet in the foreseeable future. Hell, I'm pretty sure we're not expecting to have personnel exceeding 127yo anytime soon.

(Note, however, that counting occurrences is in principle at least O(log n) space and, without a bit of cleverness, likely O(n log n) time—your integers need to be O(log n) wide to count that big!)